1. Field of the Invention
The present invention is related to oil drilling equipment, and more particularly, to an apparatus having improved interlocking units to restrain cables which transfer electrical, hydraulic and compressed-air power to the oil derrick top drive. Multiplicity of such cables are combined into a service loop.
2. Description of the Prior Art
Referring to FIG. 1, there is illustrated a standard oil derrick having a top drive drilling system which has a notation number of 3 in FIG. 1, is a common piece of machinery in an oil well drilling tower 1 in the oil drilling industry. The top drive 3 includes an AC or DC motor or a hydraulic motor which is connected to a speed reducing (torque increasing) gearbox, so that it can rotate the drill pipe to bore an oil well. The top drive is mounted in the drilling derrick and travels up and down under a control of a piece of traveling equipment 2.
Referring again to FIG. 1, there is illustrated an umbilical system 6 which is commonly called service loops. The service loops 6 are part of hoses 5 of the machinery in the oil well drilling tower, where each of the hoses transfers the respective electrical, hydraulic and compressed-air power to the top drive. There are various combinations of hoses, wires and cables that pass through the inside diameters of the service loops. Most top drives utilize a combination of two to four service loops which have approximately equal length. Each service loop at one end is attached to the derrick (or mast) 8, and at the opposite end is connected to the top drive 3. As the top drive travels up and down, the service loops move accordingly up and down in the longitudinal direction. In addition, they have a bending movement in the transverse direction, which forms the respective bend radii.
The service loops 6 of the hoses vary from about 2 inches to 7 inches in diameter. In addition, there are also variations of the hose structure and materials according to their usages in the drilling process. For example, a hydraulic pressure could be up to 3000 psi, and therefore, a hose to transfer the hydraulic fluid must be mechanically enhanced by having a sufficient thickness and an appropriate material structure. In general, the service loops have a composite structure to achieve reinforced mechanical properties. The composite structure is comprised of an inner liner, a middle braid and an outer liner. The inner and outer liners are made of thermoplastic materials or rubber. The middle braid is the composite of the thermoplastics and enhanced polymeric threads or metal wires. Therefore, the mechanically enhanced hoses have large longitudinal rigidities.
It will be appreciated that due to the variations of the hose diameters, material and structure which all affect the longitudinal flexibility of the hoses, each service loop does not always have the same bend radius. The hoses having a smaller diameter usually have a smaller bend radius, and the hoses having a larger diameter have a larger bend radius. For example, in general, hoses with two inches in diameter will have 30 inches in bend radius, hoses having three inches in diameter will have a bend radius of 42 inches, and hoses having four and half inches in diameter will have a bend radius of 48 inches. Therefore, the bottoms of the service loops travel in different paths when all the loops having the same length travel in the longitudinal direction.
The variation in paths during operation of the machinery causes the loops to become entangled. When this happens, loops with the larger diameter have the tendency to force loops with the smaller diameter into unnatural positions, which results in premature failure of the loops with the smaller diameter. In this situation, an environmental condition such as a strong wind also plays a factor to accelerate the failure of the loops. In addition, in some cases two or more loops with the smaller diameter can displace a loop with the larger diameter, which can cause problems including broken loops.
If the loop failure happens, it will not only cause a loss in economic value due to costs to replace the damaged loops and down time for replacing the loops, but also create a hazardous situation such as leakage of the high pressured air or fluids to machine operators. Therefore, finding a solution to this problem becomes an industry priority.
The present inventor has developed one solution to the above problem which as described and claimed in pending patent application Ser. No. 12/157,093, is an apparatus for flexibly restraining service loops in an oil derrick to prevent entangling of the loops. The apparatus is comprised of a plurality of identical apparatus, wherein each apparatus is positioned at a different longitudinal level to restrain the service loops. Each apparatus is comprised of a plurality of interlocking units, wherein each unit is comprised of a central steel ring which is adhesively bonded to a braid of a service loop penetrating therethrough and exteriorly affixed to first and second interconnecting rings. A first flexible cable and second flexible cable connect the respective first and second interconnecting rings of the units of each apparatus. Therefore, the significant improvement disclosed and claimed in this pending application provided service loops which were flexibly restrained to facilitate a uniform path and bend radius when the service loops travel longitudinally during operation of an oil well drilling machine. This improvement provided a significant reduction in damage to the service loops during operation.
The invention in application Ser. No. 12/157,093 required retrofitting the service loops by opening up the outer covering and installing the improvement. This could not be performed on site in the field and required installation at an off-site location. The present inventor addressed this problem in pending continuation-in-part application Ser. No. 12/590,635 wherein the interlocking units can be assembled over the outer covering of the service loops and therefore can be installed on-site.
These two pending applications by the same inventor have provided significant improvements in cable restraint systems for oil derricks. However, it has been discovered that sometimes the present inventor's prior inventions may create the following problems:                (1) when cables are encased in an outer hose, the heating from the cables is trapped, and therefore the ampacity of the individual cables must be reduced;        (2) the outside diameter of the outer hose limits the bend radius of the service loop; and        (3) if a cable or hose fails, the individual cable or hose cannot be replaced on site.        
In order to overcome the above limitations, some top drive manufacturers decided to hang individual cables and hoses in the derrick, forgoing the use of an outer hose. In order to restrain these individual cables and keep them from blowing all over the derrick, these top drive manufacturers started to tie the individual cables together using various clamps, and in some cases, a cable track. However, these clamps and cable tracks had the following disadvantages:                (1) the clamps are made of pieces of wood or rubber bolted together. If they come loose, they can fall and injure an oil derrick worker;        (2) sometimes the clamps wear through the cable insulation causing cable failure;        (3) in appearance, these devices are unattractive;        (4) when a steel cable track is used, the material holding the cables (or hoses) can wear through the cable insulation resulting in a major electrical short and other electrical problems when the high voltage line in the cable and the grounded steel cables of the cable track come in contact with each other. The cable tracks are made of steel with the electrical cables and hydraulic hoses tie-wrapped or clamped to the steel cross supports. The constant flexing wears at the electrical cable insulation and eventually wears through. 600 VAC and 1800 amps will make a large electrical spark;        (5) the steel cable tracks have a fairly large minimum bend radius, almost as large as typical hose-type service loops;        (6) cable tracks do not allow for lateral offset—the cable tracks only accept bending or offset in one direction (which is a reason clamps are used instead of cable tracks). The cable tracks are therefore subject to a lot of vibration and motion from the top drive. All this motion wears on the track links or joints; and        (7) cable tracks are bolted or riveted together and these parts may come loose and fall on workers on the oil derrick.        
Therefore, while other top drive manufacturers have provided some advantages over the patent pending designs of the present inventor which advantages include small bend radius, increased ampacity of electrical cables, and improve serviceability, they also have significant problems including falling hardware, short life, electrical sparking and shorts, and limited motion (in the case of a cable track).
There is a significant need for an improved apparatus to restrain service loops while avoiding the problems associated with the above discussed prior designs.